The standard System.Windows.Forms.TabControl component draws a border around the TabPages it contains. If you set its Dock to Fill, these borders run up to the edge of the parent control, but they're still there, taking up screen space.
In Visual Studio, if you dock two windows in the same place, you get a TabControl-like set of tabs along the bottom, but no borders along the sides.
Is it possible to get a TabControl to display its TabPages in this manner, with no wasted screen space at the sides? If possible, I'd like to avoid solutions that involve painting the control myself.
Using the standard .NET tab control, this isn't directly possible. What is the ultimate goal for this? Are you trying to simulate the same type of tabbed-MDI style display as Visual Studio? If that's the case, there are several third-party solutions available - some open source and some commercial.
The other responses about using the Anchor property in combination with setting the size so it is just a bit larger than the actual window might work, but I think it might look a bit odd visually. It should work regardless of the theme and accessibility settings, but you may end up having to programmatically set the size to be a few pixels larger than the parent.